The present invention relates in general to a contour correction system, and more particularly to a vertical/horizontal contour correction system for performing a contour correction with reference to a luminance signal and a chromaticity signal so that their vertical resolutions are identical to each other and then performing a contour correction with reference to the chromaticity signal so that its horizontal resolution is identical to that of the luminance signal.
Referring to FIG. 1, there is shown a block diagram of a conventional horizontal contour correction system. As shown in this drawing, the conventional horizontal contour correction system comprises a comb filter 1 for separating from a composite video signal CV inputted thereto a chromaticity signal C and a wide-band luminance signal Yw with a separated luminance signal Y being combined with fine vertical components contained in a color signal component.
A luminance signal Y.sub.L of low-pass component is extracted from the wide-band luminance signal Yw by passing the wide-band luminance signal Yw through a low-pass filter 2 and is applied to a subtracter 3. Upon receiving the luminance signal Y.sub.L of low-pass component, the subtracter 3 subtracts the luminance signal Y.sub.L of low-pass component from the wide-band luminance signal Yw to output a luminance signal Y.sub.B of of high-pass component to a gain controller 4. The gain controller 4 controls the gain of the received luminance signal Y.sub.B of high-pass component by an appropriate level to generate an emphasized luminance signal Y.sub.M. Then, an adder 5 adds the emphasized luminance signal Y.sub.M to the wide-band luminance signal Yw to output to a scanning line interpolator 6 a high-pass component emphasized luminance signal Y.sub.p, i.e., a signal, a horizontal contour of which has been corrected. The interpolator 6 inserts the received horizontal contour corrected signal Y.sub.p into a scanning line to output luminance signals Y.sub.R and Y.sub.I. Herein, the luminance signal Y.sub.R is a real signal being read from a memory and the luminance signal Y.sub.I is an image signal being produced by comparing the received horizontal contour corrected signal Y.sub.p with a reference signal.
On the other hand, referring to FIG. 2, there is shown a block diagram of a conventional vertical/horizontal contour correction system. The illustrated system performs vertical/horizontal, two-dimensional contour corrections respectively with respect to the original signal, or wide-band luminance signal Yw and the screen adaptable interpolation signal, or luminance signal Y.sub.I. Herein, procedures of processing the original signal Yw and the screen adaptable interpolation signal Y.sub.I are, the same and hence only the vertical/horizontal contour corrections with reference to the screen adaptable interpolation signal Y.sub.I will be described.
The conventional vertical/horizontal contour correction system comprises a line delayer 7 for delaying the received wide-band luminance signal Yw by one line and outputting a one line delayed wide-band luminance signal Yw-1 to an adder 9. The adder 9 adds the received one line delayed wide-band luminance signal Yw-1 to the wide-band luminance signal Yw to output a predetermined signal to a multiplier 10. Upon receiving the predetermined signal, the multiplier 10 performs a desired multiplying operation to output a mean luminance signal Y.sub.WL.
Upon receiving the mean luminance signal Y.sub.WL, a subtracter 19 subtracts the mean luminance signal Y.sub.WL from the screen adaptable interpolation signal, or luminance signal Y.sub.I to calculate a line difference .DELTA. E2, which is again added to the original luminance signal Y.sub.I by an adder 20. As a result, a vertical contour of the screen adaptable interpolation signal, or luminance signal Y.sub.I is corrected.
On the other hand, a band-pass filter 21 inputs an output signal from the adder 20 to extract a high frequency signal component from the output signal from the adder 20. Such extracted high frequency signal is inputted to a gain controller 22 for control of the gain thereof and is then added to the original luminance signal Y.sub.I by an adder 23. Then outputted from the adder 23 is a luminance signal Y.sub.IP in which the high frequency component is reinforced. As a result, the luminance signal Y.sub.IP is added to the chromaticity signal C separated by the comb filter 1 by a first matrix 27, which then outputs three color signals R.sub.I, G.sub.I and B.sub.I.
However, the conventional vertical/horizontal contour correction system has a disadvantage, in that an image to be displayed on the screen cannot be presented distinctly to the viewer since the system performs the vertical/horizontal, two-dimensional contour corrections only with respect to the luminance signal.